/* 基本变量 */
#wrap {
  color: #999;
  width: 100px;
  height: 100px;
  margin: 10px auto;
  background: skyblue;
  border: solid 1px red;
}
.wrap {
  color: #999;
  width: 100px;
  height: 100px;
  margin: 10px auto;
  background: skyblue;
}
.wrap-img {
  background: url("ff99e809833507c4b4ea7661b02571_180_135.jpg");
}
/*样式组合*/
.mydiv {
  width: 100px;
  height: 100px;
  border: solid 1px blue;
  margin: 10px auto;
}
/*变量运算*/
.div1 {
  width: 280px;
  height: 280px;
  color: #ffffff;
  background: #aaaaaa;
}
/*变量套用*/
.div2 {
  width: 100px;
  height: 100px;
  background: aqua;
}
.div2:after {
  content: "div2 content";
}
/*&可以拿到上一层选择器*/
.div3:after {
  content: "利用&符号拿到上层选择器.div3";
}
.div3_content {
  width: 60px;
  height: 60px;
  background: aqua;
  overflow: hidden;
}
